Porous membrane and recording medium comprising same

Abstract

The present invention relates to a porous membrane comprising multiple layers, at least one type of curable compound and at least two types of photo-initiator, wherein at least two layers each contain a the different photo-initiator. The invention further relates to recording media which comprise the porous membrane of the invention, as well as to processes for producing the membrane and the recording media.

1. A porous membrane, comprising multiple layers, and prior to curing at least one type of curable compound and at least two types of photo-initiator, wherein at least two layers each contain a different photo-initiator. 
     
     
       2. The membrane according to  claim 1  wherein each of said photo-initiators is selected from the group consisting of an alpha-hydroxyalkylphenone, an alpha-aminoalkylphenone, an alpha-sulfonylalkylphenone, an acyiphosphine oxide and combinations thereof. 
     
     
       3. The membrane according to  claim 1  wherein said membrane is essentially free from inorganic or organic particles that are capable of absorbing aqueous solvents. 
     
     
       4. The membrane according to  claim 1  wherein said curable compound is an ethylenically unsaturated compound. 
     
     
       5. The membrane according to  claim 1  wherein said curable compound comprises one or more acrylate groups or methacrylate groups. 
     
     
       6. The membrane according to  claim 1  wherein the weight ratio of said photo-initiator and said curable compound or compounds in the curable coating compositions is between 0.005 and 0.05. 
     
     
       7. The membrane according to  claim 1  wherein said membrane is formed by curing by UV radiation. 
     
     
       8. The membrane according to  claim 1  wherein said membrane comprises a polyether modified polysiloxane derivative. 
     
     
       9. A process for obtaining a porous membrane according to  claim 1 :
 providing a mixture for the toplayer comprising at least one type of curable compound, at least one type of photo-initiator, and a solvent, wherein the concentration of said curable compound(s) is preferably between 10 and 80 weight percent; 
 providing at least one further mixture of at least one type of curable compound, at least one type of photo-initiator, and a solvent, wherein the concentration of said curable compound (s) is preferably between 10 and 80 weight percent and wherein the type of photo-initiator is different from the photo-initiator used in the mixture for the toplayer; 
 applying said mixtures to a support, wherein said mixture for the toplayer is allowed to form a layer that is further away from the support than the layer that is formed from said further mixture; 
 curing each of said curable compound mixtures, thereby causing phase separation between the crosslinked compound (s) and the solvent; 
 optionally subjecting the resulting porous membrane to a washing and/or drying step to remove said solvent; and 
 optionally separating the support and the porous membrane. 
 
     
     
       10. A recording medium comprising a support and the porous membrane according to  claim 1  as receiving layer adhered to said support. 
     
     
       11. The medium according to  claim 10  wherein said support is a transparent support suitable for back-lit applications and is selected from the group consisting of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polysulfone, polyphenylene oxide, polyimide, polycarbonate and polyamide. 
     
     
       12. The medium according to  claim 10 , wherein said support is a reflective support and is selected from the group consisting of a paper support, a plastic film and a support in which a covering layer of polyolefin optionally containing a white pigment is provided. 
     
     
       13. The medium according to  claim 1 , wherein said curable compound is selected from epoxy compounds, oxetane derivatives, lactone derivatives, oxazoline derivatives, cyclic siloxanes, or ethenically unsaturated compound such as acrylates, methacrylates, polyene-polythiols, vinylethers, vinylamides, vinylamines, allyl ethers, allylesters, allylamines, maleic acid derivatives, itacoic acid derivatives, polybutadienes and styrenes. 
     
     
       14. Use of a medium according to  claim 10  for printing images or characters thereon, using Giclée printing, colour copying, screen printing, gravure, dye-sublimation, flexography, and/or ink jet printing.